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Gold to aurostibite transformation and formation of Au-Ag-Sb phases: the Krásná Hora deposit, Czech Republic

Published online by Cambridge University Press:  02 January 2018

Jiří Zachariáš  and
Matěj Němec
Jiří Zachariáš*
Affiliation:
Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Prague 2, Czech Republic
Matěj Němec
Affiliation:
Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Albertov 6, 128 43 Prague 2, Czech Republic
*
*E-mail: jiri.zacharias@natur.cuni.cz
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Abstract

Rare phases of the Au–Ag–Sb system were recognized in the Krásná Hora Sb-Au deposit (Sb 1.5–3 wt.%; Au 3–5 ppm), Czech Republic which correspond to auriferous dyscrasite (up to 7 at.% Au), auriferous allargentum (up to 34 at.% Au), and an unnamed phase with composition similar to the eutectics (E1, E2) of the experimental Au–Ag–Sb system. The dominant ore mineral is stibnite with rare native antimony, native gold and a Ag-Au alloy. Textural relationships are well established: stibnite (early) →gold → aurostibite → native antimony (late). Gold is present in four generations: Au-1 (0–15 at.% Ag) is the most abundant type; Au-2 (20–70 at.% Ag) forms thin rims along intra-grain boundaries of Au-1; Au-3 and Au-4 are rare and almost pure (∼0 at.% Ag). The formationof most of the Au-2 and of Au-Ag-Sb phases is associated with Ag-mobilization coupled with the Au-1 to aurostibite transformation via dissolution-precipitation and solid-state diffusion processes at temperatures <200°C.

Keywords

Au–Ag–Sb systemAu-Ag alloyaurostibitedyscrasiteallargentumgold depositsKrásná Hora depositBohemian Massif
Type
Research Article
Information
Mineralogical Magazine , Volume 81 , Issue 4 , August 2017 , pp. 987 - 999
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2017

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